Apollo 15

Settling down for the Journey Home

[Approaching the tenth day in the Apollo 15 mission and the Apollo 15 Command and Service Module, Endeavour has just fired its SPS (Service Propulsion System) engine to take it out of lunar orbit on a trajectory for the Earth. The three crewmen, David Scott, Al Worden and Jim Irwin, can now begin to settle down for the three day coast from planet to planet. Tomorrow, Al will leave the Command Module on an EVA (Extra Vehicular Activity) to the SIM (Scientific Instrument Module). This evening there is only housekeeping to do before they begin their rest period.]

Public Affairs Officer - "This is Apollo Control at 224 hours, 53 minutes. Apollo 15 now about 27 hundred [nautical] miles [5,000 km] from the Moon..."

224:44:47 Parker: And, Apollo 15; Houston. We'd like that Verb 49 maneuver, so we can pick up [the] High Gain [Antenna], please.

224:44:58 Scott: Roger. We just did it, Bob.

[As their spacecraft pulled away from the Moon, Al maneuvered it to an attitude that would afford the crew and the Mapping Camera a good view of the receding lunar disc. Since, during the early stages of their departure, the Moon would be moving through their field of view rather quickly, another attitude had been given to the crew that would keep the camera's aim true. Appropriate angles for pointing the HGA (High Gain Antenna) were not given until this latter, longer-duration attitude became current. The maneuver is made by entering the three given attitude angles into Verb 49. Once the spacecraft has rotated to that attitude, the HGA angles also become current and a high quality link with Earth can be achieved once they are set.]

224:45:01 Parker: Thank you. [Long pause.]

224:45:16 Worden: Hey, Houston. Take a look at the DSKY. I think those are the numbers you gave us.

[About now, a change is made to the DAP (Digital Auto Pilot), a computer routine that maintains the desired spacecraft attitude, such that any corrections will be carried out at a slower rotation rate, namely 0.2°/sec instead of 0.5°/sec.]

225:04:07 Parker: Apollo 15, Houston.

225:04:14 Worden: Go ahead, Bob.

225:04:15 Parker: Roger. We'd like to move that "Verb 49 maneuver to lunar surface photo attitude" that you'll find at 225:30 in the Flight Plan. We'd like to move that up to 225:24. Over.

[Though the Flight Plan calls for a Hasselblad camera to be configured with magazine S and the 250-mm lens, the Apollo 15 Index of 70-mm Photographs shows that this magazine was only used with the 80-mm lens at this time.]

225:25:26 Parker: Apollo 15, Houston.

225:25:31 Worden: Houston, 15. Go.

225:25:32 Parker: Roger. Be advised we'll be monitoring your maneuver here in case you get in your gimbal lock. And the High Gain [Antenna] angles [you should use] in case you lose antenna lock in the new attitude will be pitch minus 45 and yaw of 024. Over.

225:26:01 Worden: And thanks for watching it for us, Bobby. [Long pause.]

[Two possibilities are being catered for in Parker's advice. First, with respect to the current alignment of the guidance platform, there are attitudes the spacecraft should not go to for fear of reaching gimbal lock, a condition that disturbs that alignment, entailing a total realignment. The crew and controllers go out of their way to avoid this condition. Second, as they make their maneuver, it is possible that the control system of the HGA might not manage to keep the antenna pointed at Earth. As a precaution, appropriate angles are given which will allow the crew to re-establish the link.]

225:26:21 Parker: And, 15, if one of you has time, I have a few more Flight Plan updates for you.

[Al is about to realign the guidance platform. For this, the spacecraft will be maneuvered to a specific attitude which avoids gimbal lock on both the old and new alignments. These HGA angles will allow the high quality S-band link to Earth to be reestablished at the new attitude.]

[Photography of the receding lunar disc continues though it is difficult to pin down which sequence of photographs are being taken at a particular time. The Flight Plan calls for black and white magazine S to be used with a 250-mm lens but the index of images shows that the 80-mm lens was used with this camera. About half of the width of the lunar disc is covered in one image. 14 shots are taken, AS15-94-12849 to 12862, all of which overlap and a

Public Affairs Officer - "This is Apollo Control at 225 hours, 38 minutes. Apollo 15 now 4,745 nautical miles [8,788 km] from the Moon; the spacecraft velocity almost matching the altitude - 4,700 feet per second [1,430 m/s]. And at the present time, the crew aboard Endeavour are photographing the lunar surface. At the same time, the instruments in Scientific Instrument Module bay, the Gamma-ray, Alpha Particle, and Mass Spectrometer are gathering background data to be used in calibrating the data gathered in lunar orbit. A little later this evening, the crew will be turning on the X-ray instrument in the SIM bay and that will looking at extragalactic X-ray source in the constellation Centaurus. We plan to put the crew to bed in a little less than two and a half hours, now at 228 hours. At 225 hours, 39 minutes; this is Apollo Control, Houston."

225:44:43 Scott: Houston, Apollo 15.

225:44:46 Parker: Roger, 15. Go.

225:44:50 Scott: Roger Do you have any best guess on MCC-5 yet - whether or not we'll have one?

225:44:58 Parker: Stand by. It's not going to be very large.

[Mid-Course Correction 5 is an opportunity set aside to make a short burn to fine tune their trajectory towards Earth. If required, it will occur at about 238:46, just under 3 hours after they wake up tomorrow. As it turns out the velocity error will be so small that they will not bother with MCC-5.]

225:45:03 Scott: Well, the question is whether or not we have to prepare for it. And we have another request. We'd like to reschedule the UV photos presently scheduled for 239:10 to some other time, primarily because of the stowage in here. We've got most of the UV equipment already stowed beneath the rocks in prep for the EVA, and - to go in and go out of the stowage container takes a fair amount of time. And we'd like to reschedule that if it's possible.

225:45:39 Parker: Roger. [I] assume you mean after the EVA?

225:45:44 Scott: Roger.

225:45:46 Parker: Okay. Stand by.

225:45:50 Scott: Okay. This is a - this is a crowded fellow up here.

225:45:55 Parker: You guys shouldn't have brought so many rocks back.

225:46:01 Scott: Well, I guess every once in a while we wonder.

225:46:15 Scott: But we don't wonder very long. [Long pause.]

225:46:52 Parker: Okay, Dave. First of all, no problem. We can delay those UV photos until after the EVA. Second, right now midcourse 5 looks like 2 feet per second, and we do want to do it. Over.

225:47:11 Scott: Okay, thank you. That's a couple of quick answers; appreciate it. That - that will help us in our planning.

225:47:17 Parker: Okay. That is only a preliminary estimate on that midcourse 5 though.

225:47:24 Scott: That's okay. That tells us the difference between SPS and RCS kind of burns.

225:48:19 Parker: Okay. At your convenience, we'd like to verify or check the Primary Accumulator fill valve, On, until the primary accumulator quantity - that's for the glycol loop - is up to 50 to 55 percent. This is the result of a review of the EVA checklist for tomorrow. It assumes that this has already checked and that we're at the 50 to 55 percent level, so we'd like this check - you could do it tonight when you're getting ready for sleep or something.

[Sy Liebergot served as EECOM under Flight Director Milt Windler (the Maroon shift) during the Apollo 15 mission.]

[Sy Liebergot, from 2000 correspondence - "The accumulator is part of the Primary Coolant Loop which provided cooling for the cabin and electrical equipment, as well as the liquid cooling garment of the CSM EVA astronaut. The coolant was water ethylene glycol which was circulated by a pump. Essential to the coolant loop was a 'bump on the line' called an accumulator, the function of which was to absorb pressure surges, and thermal (heat) expansion and (cold) contraction of the glycol. So it was essential that it was not overfull to allow room for thermal expansion and not underfilled for thermal contraction. Too much glycol would create a hard system (high pump head pressure) and make the pump work harder. Too little fluid would cause the pump to cavitate (spin too fast). Hence the reason for keeping the accumulator at the necessary level."]

225:50:56 Scott: And if you have any other goodies you think we ought to check over, might as well do it this evening.

225:51:03 Parker: Roger, Dave. That's the only goodie we came upon... [Long pause.]

225:51:52 Parker: Stan - Stand by. Okay, 15. That's the only goodie we've had from the review of the EVA checklist for tomorrow. That - that's the only one we could find. An extra goodie that we'd like this evening sometime; if you fellows intend to use the vacuum cleaner - is for you to give us a cue when you turn it on, so we can check and watch the currents. They saw a funny on an AC bus - or an extra current load on an AC bus, and they think you were using the vacuum cleaner then. They'd like to verify that by watching it again when you use the vacuum cleaner.

225:52:27 Scott: Okay. Well, we've been using it quite often on and off.

225:52:32 Parker: Okay. Just sometime when you use it, if you give us a cue as you turn it on, that would help.

225:52:44 Scott: Okay, I - I guess we don't see any need for it this evening. And we could check it out if you'd like...

225:52:50 Parker: No, no.

225:52:51 Scott: ...pretty well. the cabin's nice and clean and I...

225:52:56 Parker: Roger, Dave. No, that's just a callout. The next time you happen to get around to feeling dirty and want to use the vacuum cleaner, give us a call if you would please.

225:53:10 Scott: Okay. We'll do it.

[Very long comm break.]

Public Affairs Officer - "This is Apollo Control. The UV photography, which Dave Scott requested we reschedule, is the ultraviolet photography, in this case of Earth, using the electric Hasselblad camera. This is an experiment being conducted to obtain ultraviolet photographs of both the Earth and the Moon to be used in study of planetary atmospheres among other things. And Scott mentioned that the equipment for that photography is stowed under the rock boxes. They've already gotten the cabin apparently set up for the EVA and requested that we reschedule it at some point after [the] EVA, when Al Worden will be going outside the spacecraft to retrieve the camera magazines from the SIM bay. And on taking a look at the Flight Plan, we reported to the crew there'd be no problem - would be no problem in rescheduling this sometime after the EVA. CapCom Bob Parker also asked that the crew, at the next opportunity when they have the vacuum cleaner out to clean up the cabin, that they give us a cue. We're interested in watching the data here on the ground, the electrical data and seeing if some current flows that we've noticed previously from the spacecraft fluctuate as we've seen them fluctuate and we suspect that the fluctuations we've seen are caused by turning the vacuum cleaner on and off. We'd like to get a cue from the crew the next time they use the vacuum cleaner to see if, in fact, this is the case. At the present time Apollo 15 is 5,519 nautical miles [10,221 kilometres] from the Moon. And as the altitude from the Moon increases, the velocity continues to drop off; down now to 4,571 feet per second [1,393 metres per second]."

[With the Trans-Earth Injection burn completed and the crew about to set the spacecraft rotating in the

PTC (Passive Thermal Control) maneuver, it is time for the guidance platform to be realigned from the TEI REFSMMAT to the PTC REFSMMAT. As with all large realignments of the platform, this is a two-stage process.]

[In the first place, Al realigns the platform to the TEI REFSMMAT using P52 in the computer as usual. This orientation matched the attitude of the spacecraft during the TEI burn and, although it is now redundant, this first realignment allows the amount of drift since the last P52 to be measured, these figures being -0.015°, -0.027° and +0.004° in X, Y and Z respectively. For this and the subsequent P52, Al aims the sextant at star 11, Aldebaran, or Alpha Tauri; and at 16, Procyon, or Alpha Canis Minoris.]

[The second realignment aims to swing the platform around to an orientation called the

PTC REFSMMAT which aids the setting up of the barbecue mode. This REFSMMAT was uplinked to the spacecraft just over an hour ago. In each case, Mission Control can watch the progress of the P52 by monitoring the DSKY (Display and Keyboard) read-outs.]

226:14:16 Worden: Houston, 15. Did you get the P52 numbers?

226:14:20 Parker: Roger. We have all your P52 numbers Al.

226:14:34 Parker: Al, we noted one of them wasn't five balls.

[CapCom Bob Parker is teasing Al about the accuracy of his star sightings, but Al's not for playing along.]

226:14:43 Worden: Say again.

226:14:44 Parker: Roger. We noticed one of those didn't have five balls on it.

226:14:50 Worden: Roger. Did you get the torquing angles on both the P52's.

226:14:55 Parker: Roger. Yes, we got them.

226:15:00 Worden: Okay. Thank you. [Long pause.]

[As part of the P52 procedure, Al uses the computer/optics system to measure the angle between the two stars that he used. The angle is compared to the true angle to present Al with the difference. It is a matter of some pride to CMPs that this difference is zero (to within a hundredth of a degree) which presents 00000, or "five balls" on the DSKY display. Five balls and four balls one (00001) were equally common during the mission with four balls two (00002 or 0.02°) appearing only occasionally. This level of error is of no consequence.]

[During the double P52 just completed, Al got five balls the first time, and four balls two on the second attempt.]

Public Affairs Officer - "This is Apollo Control. At the present time Al Worden is completing a platform alignment for Program 52. He's aligning the platform to a new set of coordinates provided by the ground and these coordinates will be used as an attitude reference by the..."

226:15:55 Parker: And, Endeavour; Houston. Over. [No answer.]

[Comm break.]

226:17:18 Parker: Endeavour, Houston. Over.

226:17:24 Scott: Go ahead, Houston; Endeavour.

226:17:26 Parker: Roger. If one of you guys has time, we have what may or may not be the last iteration on troubleshooting the Pan Camera this afternoon. Over.

226:17:38 Scott: Okay. Have at it.

[Mission Control are still concerned about the characteristics they saw from the Panoramic Camera's telemetry when it was supposed to run to the depletion of its film. Each time a problem appears in the spacecraft, a team in the SPAN (Spacecraft Analysis) Room begin dissecting and troubleshooting it, both to rectify it and to weigh up the possible consequences if it continues to impact the mission. The instructions Parker will read up are to put the camera through a well-understood set of steps so that its telemetry can be studied again.]

226:17:40 Parker: Okay, step one; we'd like to know - you - you can give us these afterwards, but the first step is to determine the status of the Service Module Sector 1 AC 2, circuit breakers on panel 181. Those are three circuit breakers. Number two is to determine the status of the Pan Camera Mode switch. Number three, after these have been done, Pan Camera Mode, Standby; Power, On, talkback barber pole for 2 seconds, then gray, and then Stereo. Number four, Pan Camera Mode, Operate, talkback barber pole for 2 seconds, then gray. Number five, operate Pan Camera until MSFN cues, or until beginning of the sleep period. And number six, on MSFN cue, Pan Camera Mode to Standby; and, after one minute, Pan Camera Power, Off. Over.

226:19:07 Scott: Okay, Bob. You clipped the first part of number 5. Say again, please.

226:19:12 Parker: Roger. Number 5 says operate the Pan Camera until the ground gives you a cue or until beginning of the sleep period. Then we'll give you a cue.

226:19:27 Scott: Okeydoke. Stand by a minute. [Long pause.]

226:19:55 Scott: Okay, Houston. SIM Sec AC 2 circuit breakers, three, closed, verified. And the Pan Camera Mode switch is in Standby. So would you like us to go to step 3?

226:20:08 Parker: Endeavour, Endeavour, this is Houston. Roger. That appears to be the problem. Stand by and I'll see what we want to do. Do we...

226:20:23 Scott: Okay.

226:20:24 Parker: Apollo 15, Apollo 15, this is Houston. Roger. Press on with step 3 from that point when convenient.

[Note that Parker has begun repeating the initial words of his call. As explained at 228:17:40, this is to overcome network communications problems. As pointed out by journal reader Dave Edwards, Dave Scott noticed about a minute ago that the beginning of Parker's sentences were being clipped. Parker immediately begins a work-around until the problem can be fixed.]

226:25:47 Parker: Apollo 15, Apollo 15, we've succeeded in using up the last of the film in the Pan Camera. You may now go Pan Camera Mode, Standby; and, after 1 minute, Pan Camera Power, Off, per step 6. Over.

226:26:53 Parker: Apollo 15, Apollo 15, Houston. We're going to take down the network line here for 20 seconds. We'll be back up with you after that.

226:27:05 Scott: All righty.

[Very long comm break.]

[Mission Control's analysis leads them to believe that a sensor switch within the Panoramic Camera is not being acted upon at film depletion. After return to Earth, it is found that the film is about 60 metres short, having been cut in the middle of the camera's penultimate frame by its retrieval from the SIM bay. Their suspicions fall on a capacitor after the flight when another camera experiences the same type of failure, which is found to be due to the capacitor. However, the situation is not so simple.]

[Often in engineering, designers will implement a particular function or feature to deal with a particular set of requirements, only to discover that their "design feature" operates in unforeseen ways when brought into the final model. This is the case with the Panoramic Camera. There is a switch that operates when the film nears depletion. After its actuation, it unintentionally inhibits the "Operate" control if the camera is placed in "Standby". The camera should have been left in "Operate" until film depletion, but no one was aware of the problem because the situation could only arise on a space-borne camera. Pre-launch configuration was such that this unusual condition never occurred.]

Public Affairs Officer - "This is Apollo Control. Now Apollo 15 is now 8,200 [nautical] miles [15,200 km] from the Moon. And the crew should be in the midst of an eat period, and we plan to put them to bed at 228 hours, or about 1 hour from now. Prior to that, they'll put the spacecraft in a stable attitude and then start it rotating slowly so that it gets equal exposure to sunlight and darkness. This is to maintain the proper temperature equilibrium. Dave Scott inquired a while ago if we were planning to do midcourse correction 5, that's the midcourse opportunity at 238 hours, 46 minutes, and the flight dynamics officer reported at that time that yes, we did plan to do midcourse correction 5 based on the preliminary data that we have, the preliminary tracking information. That burn will be about 2 feet per second which would be performed with the Reaction Control System thrusters."

[Prior to their meal break, a lithium hydroxide canister was changed with number 19 going into receptacle B and the exhausted canister 17 being stowed in compartment A4.]

[The spacecraft is maneuvered to aim the X-ray Spectrometer at Centaurus and the instrument is switched on to it can collect data during their break. Jim and Al switch places as the subject of the Surgeon's study via their biomedical harness.]

[The x-ray source known as Centaurus-A is an elliptical galaxy which was found to emit heavily across the electromagnetic spectrum. Optically, it is well known for the large band of dust that distinctively crosses in front of it.]

[Mission Control leave the crew alone for the full hour to get on with their meal. Once that is over, the X-ray Spectrometer is switched off, its covers are closed and Al maneuvers the spacecraft to the correct attitude to commence the

227:37:14 Parker: Roger, 15. We see you maneuvering to PTC, and we're requesting that you not maneuver to PTC until the SIM bay covers are closed. I don't know whether they're closed at the moment or not.

227:37:33 Scott: Roger. They're closed up.

227:37:39 Parker: Understand. And if you fellows...

227:37:41 Scott: We're just following down through the Flight Plan.

227:37:44 Parker: Good. We weren't sure where you were. If you fellows are through eating, we have two or three calls to send up to you, when it's convenient. [Long pause.]

227:38:34 Parker: Apollo 15, Apollo 15; Houston. You can go to T-stop with the Mapping Camera now. And that would be - to follow the checklist for pages 1-39, steps - section 6, 7 and 8; first one being Mapping Camera, On to Off, 30 seconds, and then Standby. Over.

227:39:23 Worden: Houston, 15.

227:39:25 Parker: Apollo 15, Apollo 15; Houston. Go.

227:39:28 Worden: Houston, 15. Okay...

227:39:31 Parker: Apollo...

227:39:32 Worden: ...Listen, Bob. Is this the T-stop on the Mapping Camera photo PAD at 224:10?

227:39:37 Parker: Apollo 15, Apollo 15, that's a Roger. [Long pause.]

[The Mapping Camera PAD that Al refers to only had an absolute T-start time which had been read up at 222:49:49. The T-stop time was replaced by an instruction to stop the camera on the ground's instructions - a MSFN cue - which the ground have just given.]

227:40:31 Scott: Okay, Houston. Go with the rest of the updates to the Flight Plan.

227:40:36 Parker: Apollo 15, Apollo 15; Houston. Roger. We - want to remind you, when you go into PC - TC, to follow the block in the Flight Plan for the usage of quads, rather than the section in - in the checklist where it calls out to disable all jets on two adjacent quads. This is to avoid contamination of the Mass Spec. It's just to remind you to follow that little box in the Flight Plan. Over.

[The last time Al executed the PTC maneuver, was during the translunar coast, before the SIM bay door had been jettisoned. Now he has to be careful that the hot gases from the RCS thrusters do not impinge on these exposed instruments, therefore, he must follow steps in the Flight Plan rather than in the checklist.]

227:41:07 Scott: You mean that little box on page 3-343?

227:41:12 Parker: Apollo 15, Apollo 15, that's a Roger.

227:41:17 Scott: Okay. We'll follow that little box just like it's in the Flight Plan. Go ahead with your - the rest of your updates.

227:41:23 Parker: Apollo 15, Apollo 15. Roger. On - one discussion here on the UV photos which we're delaying until after the EVA, it looks like the last chance to get these photos is at 246:15, which is about 3 or 4 hours after the nominal end of the EVA. We'd like to propose that for your consideration. Over.

[At 225:45:03, Dave requested that a series of UV photos be delayed as the equipment had been stowed beneath other items in preparation for tomorrow's EVA.]

227:42:29 Scott: Okay, Bob. Do you have anything else to add to the Flight Plan.

227:42:34 Parker: Apollo 15, Apollo 15; Houston. Roger. One more item we just got is a request that now that the covers on the X-ray are closed, we're requesting X-ray, On, for 10 minutes and then Off. Over.

227:42:51 Scott: Okay, X-ray, On, for 10 minutes and then Off.

227:42:57 Parker: Apollo 15, Apollo 15, the posit - the last [switch] position should be Standby rather than Off. Over.

227:43:07 Scott: Roger. Standby. [Long pause.]

227:43:52 Scott: Okay, Houston. The X-ray is On, and we'll turn it Off in 10 minutes. Anything else?

227:44:00 Parker: Apollo 15, Apollo 15; Houston. That's a Standby in 10 minutes. I believe you understand that, Dave, anyway. And I believe that the next...

227:44:11 Scott: Roger.

227:44:12 Parker: ...thing we will want from you is a call when you're ready to go to sleep. And we will verify all systems at that time so we can get a solid goodnight, rather than tagging on, again like last night.

227:44:27 Scott: Roger that.

[Comm break.]

227:46:29 Parker: Apollo 15, Apollo 15; Houston. We see you cycling through the DAP. We suggest you need a zero in R2 to get B/D roll. Over.

[Very long comm break.]

[The status of the

Digital Auto Pilot is set by two values stored in registers in the computer. Mission Control is monitoring Al's use of the DSKY and they help to catch any problems with setting the PTC roll going. The alternative steps given in the Flight Plan for this PTC include the use of the B and D RCS quads to start the roll. This pair of opposed quads are chosen as they direct their exhaust away from the SIM bay. They are enabled by entering 0 in the first position of Register 2 in the DAP routine.]

Public Affairs Officer - "This is Apollo Control at 227:55 minutes. The crew is - aboard Apollo 15, is presently getting the spacecraft set up for the Passive Thermal Control where they will be rotating at about 3 revolutions per hour. This is the standard set up used during the sleep periods to maintain proper thermal equilibrium on the spacecraft. And at the present time, Apollo 15 is 10,488 nautical miles [19,424 km] from the Moon. The spacecraft velocity: 4,129 feet per second [1,259 m/s]. ..."

227:57:08 Worden: Houston, 15.

227:57:11 Parker: Apollo 15, Apollo 15. Go.

227:57:16 Worden: Hey, Bob, you didn't update the - arrange the load in the P20 for PTC. Was that meant to be updated to .375 or shall we leave it at .35?

[On the first day of the mission, Al had some trouble getting a stable PTC roll going. One of the changes given by Mission Control to fix the problem was to make the spacecraft spin slightly faster, at 0.375°/second.]

227:58:54 Worden: Yes, Bob. We're trying to retract the Mapping Camera. But the time has been well exceeded and we still have the barber pole indication.

227:59:06 Parker: Apollo 15, Apollo 15. Stand by. [Long pause.]

[The first time the Mapping Camera was used in lunar orbit, its extension and retraction times were as expected. Subsequently, the times have extended until now when the mechanism appears to be stuck in the deployed position. This is not a problem for the remainder of this mission but needs to be fixed before Apollo 16 in case a similar problem affect spacecraft operations.]

227:59:59 Parker: Apollo 15, Apollo 15. We'd just as soon you didn't spin up quite yet. We still think the rates are a little high. Over.

228:01:34 Parker: Apollo 15, Apollo 15; Houston. Concerning the Mapping Camera retraction problem, the question is did you get a barber pole during the Alpha/X-ray cover procedure? Over.

228:02:03 Irwin: You ought to amplify your question there a little bit, Bob. You mean when we are - operating the covers? [Long pause.]

228:02:35 Parker: Apollo 15, Apollo 15; Houston. Jim, the question basically is, did the barber pole, did the talkback function properly when you just closed the alpha/X-ray covers? Over.

228:02:52 Irwin: Yes. Dave said it works fine. [Long pause.]

228:03:43 Parker: Apollo 15, Apollo 15; Houston. Jim, stand by on that. We got your last answer, and they're working on it.

228:03:53 Irwin: Okay. I think I'll take the - go out of the Retract position on the switch and just wait for your word.

228:04:01 Parker: Apollo 15, Apollo 15. That sounds good to me, Jim.

[Long comm break.]

[Mission Control suspect that there is mechanical interference between the camera and the instrument covers. Al will have a chance to look at it tomorrow but, in the meantime, the SPAN room continues to troubleshoot the problem. However, the problem still had not been solved according to the post-mission report dated 5 months after the flight.]

228:09:45 Parker: Apollo 15, Apollo 15; Houston. We'd like to hold off on PTC a little bit longer until we get this Mapping Camera business straightened out. And, Jim, for some troubleshooting on this, we'd like to have you check on panel 181, the Main A circuit breaker, closed, and the Deploy/Retract switch in the Retract position. And on panel 278, the Deploy Main A circuit breaker, closed. Over.

228:10:26 Irwin: Those two circuit breakers and the switches are verified, Bob, closed.

228:10:32 Parker: Apollo 15, Apollo 15. Copy.

[It's getting past the time for the crew's rest period to start and they are getting on with the items in the pre-sleep checklist. First of all, Jim reports on the crew status and the onboard read-outs.]

228:10:40 Irwin: And the presleep checklist: been no medication today. Onboard readouts are Bat C, 37; pyro Bat A, 37.3; pyro Bat B, 37.3. On the RCS, it's 56, 55, 54, and 55. And I guess, after we get PTC squared away, we'll give you the E-memory dump.

[It is interesting to compare the RCS quantity readings from the spacecraft, currently averaging 55%, to those coming from Mission Control which were averaging 46% this morning and will be 41% tomorrow morning. This is in light of the fact that the secondary tanks were brought online earlier today, giving an accurate data point of 43%. Mission Control have far greater resources to monitor and factor helium temperature, pressure, RCS usage and system history into an accurate reading, whereas the read-out in the CM is derived only from the temperature and pressure of the helium used to pressurise the system.]

228:11:12 Parker: Apollo 15, Apollo 15; Houston. Copy the crew status and the onboard readout. And stand by on the E-mod; we may ask you for that before PTC, but we'll be back with you on that in a minute.

[Comm break.]

[Other items to be dealt with are to chlorinate their water supply, verify the status of various spacecraft systems and prepare the spacecraft communication system for their sleep period.]

228:12:48 Scott: Houston, 15.

228:12:56 Parker: Apollo 15, Apollo 15; Houston. Go.

228:13:02 Scott: Roger. Un - unless you got a solution for the camera now, why don't we troubleshoot it in the morning and get on with our evening powerdown. Okay?

228:13:13 Parker: Apollo 15, Apollo 15; Houston. That's a Roger. We've just come to that conclusion ourselves down here. We're ready for an E-mod dump before the start of PTC, please.

228:13:29 Scott: Okay. It's on the way. [Long pause.]

228:14:18 Parker: Apollo 15, Apollo 15; Houston. One last attempt on the Mapping Camera. We suggest you try Mapping Camera doors, Open, then Retract, and then doors, Close, if successful on the retract. And you can do that while - after you start up PTC, if you like.

[Four hours ago, the boom carrying the Mass Spectrometer was deployed and the instrument allowed to outgas. Now it is operated throughout the rest period before being switched off just prior to tomorrow's EVA. The data gathered during this spell is primarily intended for comparison with that taken from lunar orbit in a bid to tease out indications of a lunar atmosphere.]

228:16:08 Scott: Roger.

228:16:16 Parker: Apollo 15, Apollo 15, Houston is out for the evening.

228:16:25 Scott: Don't go too far out, though.

228:16:31 Parker: Apollo 15, Apollo 15, our ever watchful eye will be on you while you sleep.

Public Affairs Officer - "This is Apollo Control. Spacecraft now is beginning the Passive Thermal Control rotation. As we rotate from one antenna to another Omni antenna, we'll pick up some noise from time to time during the evening."

228:17:12 Parker: Apollo 15, Apollo 15; Houston. You called just as we lost and locked onto the high - onto the Omni.

228:17:40 Worden: Okay, Bob. It just didn't look like I got quite as much rate when I entered on that as I expected.

[Very long comm break.]

Public Affairs Officer - "Our Communications Engineer reports that the crew have configured the communications circuits on board the spacecraft now for their sleep period and we do not expect to hear from them further during this 8 hour rest period. We've had some questions [from journalists] on the double calls, the repetition of the call Apollo 15, by the CapCom. And the Network Controller reports that this is being done because of a weak or low level we've got on the landlines from Houston to Madrid. And normally the tone that is sent out in conjunction with the CapCom's call, the bleep that usually precedes the call is used to key the ground transmitter so that it's in the proper configuration for uplinking the voice communications. The problem we're having with the lines gives us a low level at Madrid and the beep is not getting through. At least not with sufficient strength for the transmitter to key the transmitter. So, in order to key it, the CapCom repeats the call Apollo 15. The first Apollo 15 keys the transmitter and the second one goes up to the spacecraft. This is a relatively minor problem; the network controller knows it can be readily remedied once we've completed our presleep checklist and have gotten the crew off to - off to sleep and don't expect any further air to ground communications. They'll simply take the line down, make the necessary corrections to it, and within a matter of minutes have the situation remedied. It was decided to use the so-called manual keying technique with the CapCom repeating the Apollo 15 call, simply because it was a simple procedure and because we were close to the sleep period when we could do the maintenance on the lines that were necessary. Apollo 15 at the present time is 11,534 nautical miles [21,454 km] from the Moon and the spacecraft velocity is 4,078 feet per second [1,243 m/s]. The crew reported, prior to beginning their rest period, that the Mapping Camera, which extends out from the SIM bay on a rail system, had not, apparently, not retracted. They have an indicator in the spacecraft cockpit that tells when this camera has retracted and the indicator showed that it had not come back in. After checking the situation with the Orbital Science Officer, it was decided that it would do no serious harm to leave the camera deployed. The only concern would be that the temperature could possibly go higher than desired. However, the temperatures that we've seen from the Passive Thermal Control mode previously indicate that this should not be a problem; we would not expect the camera to become too warm and more importantly the film cassette. And the thermal experts feel that the temperatures that it would encounter in the SIM bay during the Passive Thermal Control mode would not cause us any problem. So we've elected to follow the suggestion of Dave Scott and leave the camera deployed until tomorrow and work on the problem then. One suggestion that the Orbital Science Officer had is that perhaps the camera retraction mechanism had become too cold and is for that reason failing to retract and perhaps in the Passive Thermal Control mode, when the temperature will warm up somewhat, it'll free whatever it is, is causing the problem, and we'll be able to retract it in the morning. At 228 hours, 24 minutes, this is Apollo Control, Houston."

228:41:49 Parker: Apollo 15, Houston. Over. [No answer.]

228:42:28 Parker: Apollo 15, Houston. Over. [Long pause.]

228:43:03 Worden: Houston, 15. Go.

228:43:06 Parker: Roger, 15. Would you believe that we have one more call on the Pan Camera. We do not show Pan Camera Power to Off, please, and unfortunately, that means that we might heat up the film too much. So we would like Pan Camera Power to Off. And guys, as long as you're down there, would you mind trying Mapping Camera, Retract once more. 15, we see a certain rise in temperature there which may mean that it was frozen; it'll improve. And we do not see any - the Mass Spec. configuration yet. And a progress report on your PTC says it's about 60/40, but it'll - it will last the night.

[Long comm break.]

228:48:17 Worden: Houston, it doesn't look like the Mapping Camera is going to come back in. What's the problem if it's left out?

228:48:24 Parker: 15, Houston. Would you believe we've just determined that it doesn't seem to be a problem if it stays out overnight.

228:48:35 Worden: Great. Then I guess we can call it quits for the night. Okay?

228:48:40 Parker: I sure hope so.

228:48:44 Scott: [Laughter.] Okay, good night.

228:48:46 Parker: 15, we don't have TM on you right now. Is the Mass Spec. taken care of?

228:48:54 Scott: Roger. The Mass Spec's taken care of. There's one switch out of position. And the Mapping Camera is going to go to Off.

228:49:11 Parker: Roger. Copied, Dave. We'll try again.

228:49:19 Scott: Okay.

[Long comm break.]

228:58:50 Parker: Apollo 15, Houston. In the blind, no need to reply. Our Pan Camera data still shows Power, On. This is the middle switch in the bottom row. The Power Boost switch should be in the center off position. No need to reply. Over.

[Very long comm break.]

Public Affairs Officer - "This is Apollo Control at 229 hours, 30 minutes. The Flight Surgeon reports that the crew appears to be getting to sleep at this time. We have biomedical data on Command Module Pilot Al Worden and his rates indicate that at least he is approaching sleep. Apollo 15, at the present time, is 14,244 nautical miles [26,380 km] from the Moon and the velocity is down now to 3,976 feet per second [1,212 m/s]. During this rest period we plan to come up with hourly status reports and in the - in between status reports we will have lines down with tape recorders running to record any unexpected conversation with the crew. The spacecraft is in a stable passive thermal controlled attitude right now, that will be one of the activities here in Mission Control tonight, to watch that attitude and see that it does not diverge from acceptable limits. And assuming that the attitude stays stable, the spacecraft rotating at approximately 3 revolutions per hour and not diverging from the preset attitude, we would not plan to call the crew this evening. At 229 hours, 32 minutes, this is Apollo Control."